1. Field of the Invention
This invention relates generally to inkers of the kind used to deposit small quantities of ink upon selected portions of semiconductor wafers during electrical performance testing of such wafers, and more particularly to a disposable inker cartridge and associated holder for use with such inking devices.
2. Description of the Prior Art
Manufacture of semiconductor devices called integrated circuits is commonly carried out in a batch process involving a large disc-shaped slice of nearly pure, crystaline silicon generally referred to as a wafer. Each such wafer contains hundreds, and possibly even thousands, of completely independent circuits. At the completion of conventional chemical processing of a wafer, each independent circuit is tested and classified by high speed electrical and mechanical test equipment. In order to permit a visual recognition of the determined classification of each individual circuit on a wafer, it is conventional to deposit a small quantity of ink upon at least certain ones of the circuits at the completion of their testing. For example, a defective circuit may be marked with ink while the absence of an ink droplet usually signifies that the particular circuit meets required specifications. Various colors of ink can be employed to determine various levels of performance classifications for a specific circuit, with red ink being typically used to indicate a failing or non-functioning circuits.
Following such testing, each wafer is cut by methods known in the art into individual integrated circuits, sometimes referred to as a "die." In this process, the circuits are physically separated based on the presence and color of ink, if any, deposited on the die. Further processing is performed on the circuits based on the performance classifications and functionality determined at the wafer level testing stage.
The inker devices presently employed to deposit ink drops on semiconductor wafers involve a "soft contact" on the wafer of a piece of nylon filament, and the like, passed through a reservoir of ink. The filament is caused to momentarily contact a specific circuit of a wafer being tested so as to leave a small deposit of ink on the wafer. In a typical arrangement now being used, the filament is extended through an element similar in configuration to a hyperdermic needle and terminating in a needle portion into which the filament extends. The upper portion of this needle-like device forms a cup in which must be deposited a quantity of ink. The cup forms the reservoir of ink which is carried to the wafer by the filament. The latter is supported for reciprocating movement by a plunger-like member through which the element passes and which functions as the moveable core of a solenoid coil. Thus, selective actuation of the solenoid coil will move the plunger-like member, possibly against the bias of a return spring, in a downward direction so as to move the tip, or lower end, of the filament into contact with the surface of a wafer being tested.
The known apparatus as discussed above has several drawbacks, primary of which is the relatively small capacity of the permanently attached reservoir, which requires the unit to be stopped and frequently refilled with ink. Further, the filament often jams during operation, requiring the apparatus to be shut down for cleaning, refilling of ink, and necessary readjustment. In any event, the apparatus requires cleaning at the completion of each operating shift and a stock of springs, filaments, ink, and other items which need be replaced periodically. As a result, the presently employed equipment has been found relatively expensive and difficult to use, with much ink mess resulting from the necessary refilling and cleaning of the ink reservoir.